[sdiy] Multi Segment Envelope Generator

[patchell]

    The heart of the circuit is actually just a "glide" (U2A,U3A).  The
glide rate has an exponential control on it (Q1,Q2).  The reset of the
circuit is more or less just an 8x2 sequencer.  One channel controls the
glide rate, the other controls the level it glides to.  When the glide
level is equal to the glide output, it goes to the next step.  All of
this, is of course, controlled by the logic.

    The logic could probably actually fit inside of a single 22v10.  The
problem I have with doing this is I have found the newer pld's to be
less than rugged.  The logic could also probably be done with a PIC or
AVR...but, I am too lazy.

    As far as the comparators oscilating...that is one reason I just
used regular opamps as the comparators.  Less bandwidth.  I used a
similar comparator on my 8x2 analog sequencer and it seemed to work
pretty good.

Tim Ressel wrote:

> Jim,
>
> This is an interesting circuit. It is similar to an
> ADSR I tried to make. Basically a 4-segment version of
> yours. From the schematic, it looks like this is an
> exponential generator meant for a linear VCO. Yes? If
> so, it looks pretty easy to make it linear.
>
> I had a lot of trouble with the comparators on the
> version I tried. They tended to oscillate from noise
> when the inputs were near each other. This caused the
> logic to go nuts. I never went back to see if I could
> fix it.
>
> Keep on truckin', and keep us informed!
>
> --TR
>

--
 -Jim
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